Samsung 990 PRO 2TB: Performance Degradation After 7B2QJXD7 Firmware Upgrade - Capacity-Specific Bug?

[SFdrifter]

PLEASE NOTE THAT THIS FIRST POST WAS MOSTLY INCORRECT -- I MISINTERPRETED SLC CACHE EXHAUSTION FOR POOR PERFORMANCE; I DO NOT BELIEVE THERE IS A FIRMWARE BUG INVOLVED

I'm reporting an apparently capacity-specific firmware bug affecting Samsung 990 PRO 2TB drives after updating to firmware 7B2QJXD7. My 4TB 990 PRO with identical firmware performs normally.

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**AFFECTED DRIVE:**
- Model: Samsung SSD 990 PRO with Heatsink 2TB (used as system drive with 5 partitions)
- Serial: S7DRNJ0XC08579H
- Firmware: 7B2QJXD7 (upgraded from 4B2QJXD7)
- System: Arch Linux, AMD Ryzen 9 9900X

**COMPARISON DRIVE (NORMAL):**
- Model: Samsung SSD 990 PRO 4TB (used as data drive with 1 partition)
- Serial: S7DSNJ0X912378T
- Firmware: 7B2QJXD7 (upgraded simultaneously with the 2TB SSD)

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**PERFORMANCE DEGRADATION (FIO BENCHMARKS):**

**2TB Drive - BEFORE firmware upgrade, using 4B2QJXD7:**
✓ Sequential Write: 6,650 MB/s
✓ Random Write: 4,436 MB/s (1,135K IOPS)
✓ Sequential Read: 6,650 MB/s
✓ Random Read: 2,970 MB/s (760K IOPS)

**2TB Drive - AFTER firmware upgrade, using 7B2QJXD7:**
xx  Sequential Write: 1,478-3,691 MB/s (45-78% LOSS)
xx  Random Write: 1,375-1,460 MB/s (68-70% LOSS) ← CRITICAL
✓  Sequential Read: 6,752-7,007 MB/s (normal)
xx  Random Read: 2,369-2,582 MB/s (13-20% loss)

**4TB Drive - AFTER firmware 7B2QJXD7:**
✓ Sequential Write: 6,577 MB/s (NORMAL)
✓ Random Write: 4,435 MB/s (NORMAL - matches 2TB baseline!)
✓ Sequential Read: 6,687 MB/s (NORMAL)
✓ Random Read: 4,594 MB/s (EXCELLENT - better than 2TB baseline!)

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**TESTING METHODOLOGY:**

To isolate the issue, I performed extensive testing:

1. Tested across multiple partitions (root, home, data)
2. Tested from Live USB (eliminating OS activity)
3. Tested both drives with identical parameters
4. Monitored temperatures during tests

**KEY FINDINGS:**
- Performance degradation occurs on ALL partitions of 2TB drive
- Live USB testing (no OS) still shows degraded performance
- 2TB drive runs 26°F hotter than 4TB (113°F vs 87°F)
- Higher temp suggests excessive write amplification?
- 4TB drive with SAME firmware performs perfectly
- Both drives updated simultaneously
- Both have similar write endurance (~22-23TB)

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**TEMPERATURE COMPARISON:**
- 2TB (Problem): 113°F / 45°C (elevated)
- 4TB (Normal): 87°F / 31°C (normal)

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**POSSIBLE IMPLICATIONS**

Is this a **capacity-specific firmware regression** affecting 2TB 990 PRO models?  Does the 7B2QJXD7 firmware have different code paths for different capacities, and does the 2TB implementation have a critical bug in random I/O handling?

The elevated temperature on the 2TB drive suggests the firmware is causing excessive internal operations (write amplification, garbage collection, etc.).

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Dear Samsung -- 

1. Can you please confirm this capacity-specific bug?
2. Can you investigate why 2TB apparently differs from 4TB implementation?
3. Can you provide a firmware fix (8B2QJXD7) or rollback capability?
4. Can you provide guidance for affected users?

**Has anyone else experienced this after updating 2TB 990 PRO to 7B2QJXD7?**

I have detailed benchmark logs, SMART data, and test results available as requested.

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**System Details:**
- OS: Arch Linux (kernel 6.x)
- Motherboard: AsRock x870e Taichi
- Testing Tool: fio 3.39
- Test Parameters: libaio, direct I/O, various block sizes

[Memory Product Expert -1]

Hello SFdrifter,

Have you contacted Samsung support for warranty service / testing ?
It maybe best to have the SSD sent to a Samsung service center to confirm the issue and make sure that this is not a hardware problem that was caused by the firmware update process and any potential errors while updating. 

The update 7B2QJXD7 was released around June of 2025, so many users have already updated and have reported no issues, this included both 2TB and 4TB models 
 

[Memory Product Expert -1]

Just for further review, Below are my current speeds. 
Random Write for me is a little low, but this is due to motherboard and some OS background activity. 

Setup:
Firmware - 7B2QJXD7
SSD - 990 PRO is 2TB 
OS - Windows 11 PRO 
Motherboard - MSI X670E Tomahawk 
Processor - AMD RYZEN 9 7900X

[SFdrifter]

You're showing better performance than I ever realized, and certainly much better than I see now.  Since I first posted, performance has further degraded over the past 18 hours, so I'm concerned that failure is imminent even though SMART data looks ok.

Doing an RMA means replacing my system drive beforehand, and I've purchased an SN8100 as a replacement.  There's already 26TB in my PC, so I won't be RMA'ing this unit:  I won't get my money back, and I don't need another 2TB drive, especially taking up an NVMe slot.

Thanks for your input. 

[SFdrifter]

In investigating further, I noticed that SMART data for the 2TB and 4TB 990 Pro SSDs report the same number of power cycles (the drives were both installed at the initial build in February) but much different power-on hours. Similar results were also apparent from earlier tests in September using the older firmware.

8 Sept 2025; 4B2QJXD7 firmware

metric // nvme0 (4TB) // nvme1 (2TB) // ratio/delta

Power Cycles // 689 // 689 // 1.0x

Power On Hours // 945 // 2,108 // 2.23x

Temperature // 33°C // 39°C // +6°C

Controller Busy Time // 978 // 1,899 // 1.94x

23 October 2025; 7B2QJXD7 firmware

metric // nvme1n1 (4TB) // nvme0n1 (2TB) // ratio/delta

Power Cycles // 821 // 821 // 1.0x

Power On Hours // 1,025 // 2,447 // 2.39x

Temperature // 31°C // 45°C // +14°C

Controller Busy Time // 1,118 // 2,224 // 1.99x

The odd counting of power_on_hours is either intentional or it's a bug spanning at least 2 firmware versions.  Weird, eh?

Regardless, the firmware update seems to have caused thermal issues.

Temperature comparison (both drives in same system):
- 8 Sept (4B2QJXD7): 2TB=39°C, 4TB=33°C (6°C difference)
- 23 Oct (7B2QJXD7): 2TB=45°C, 4TB=31°C (14°C difference)

The 2TB drive's temperature increased by 6°C after the firmware update, and the temperature delta between drives more than doubled.

This thermal increase, combined with the 70% performance loss, suggests that the 7B2QJXD7 firmware is causing the 2TB drive to work much harder internally, possibly due to excessive write amplification or garbage collection activity.

[Memory Product Expert -1]

Hello SFdrifter, 

If this was all caused by a bad firmware, wouldn't all users with the same firmware version show similar results to you? 

If you are still seeing issues, it would be a good idea to have your SSD tested by Samsung's warranty team, maybe then can confirm there is an issue and provide a replacement or further escalate if something else is found.

[SFdrifter]

Fair enough...I've got a hectic upcoming 4-6 weeks, but I'll RMA it as soon as I can.  I suspect, however, that not every user benchmarks their SSD after each FW upgrade and not every user has both a 2TB and 4TB 990 Pro installed at the same time.

Again, thanks for your attention.

[useroIUpCVJ7VK]

That's good to know. I haven't updated my firmware to the 7B2QJXD7 because apparently the magician software doesn't work with the vmd interface and has never worked with it so I'm told. Even though I've received 2 fw updates through it, I was told I got lucky. Lol
Now if I want to update my firmware I have to do so manually. This will be the one and only samsung drive I have ever bought. I will be replacing this drive. I knew I should've went with crucial.

[Memory Product Expert -1]

Hello useroIUpCVJ7VK,

Well VMD can be turned off unless you need it for something specific for your work or something.

Otherwise, lots of companies like Dell and Lenovo have guides for download on their website on how to turn off VMD, its typically just a setting within your computers BIOS settings.

This is because the computer manufactures know that VMD is not needed in most cases, especially for normal users.

[useroIUpCVJ7VK]

Oh so I have to change something that was working fine so Samsung doesn't have to fix their software. I use this for music production and I am not about to do a fresh install to turn off Vmd and have to reinstall 100s of plugins. I have been getting updates from Magician for a year and have updated the firmware twice through Magician. This is definitely something they could fix. If I have to do a total reinstall why would I keep this drive, I will just buy a new drive from Crucial where this isn't an issue. I will never buy another Samsung drive again. And after this, I am debating changing all my Samsung products.